UP Aerospace has been flying since 2006, albeit at low flight rates, so I wouldn't call that early operation.
T-Minus Engineeringhttp://www.t-minus.nl/"The T-Minus DART is a system for fast and low-cost probing of the upper atmosphere. A certain part of the atmosphere is hardly investigated until now. At altitudes between 50 and 120 km, the air density is too low for balloons to float, and too high for satellites to maintain their orbit. Sounding rockets can be used to perform in-situ measurements, but these are usually too expensive for simple and frequent missions."
Another one left out: bluShift Aerospace (https://www.blushiftaerospace.com/) has been developing at least three different suborbital rockes according to their website (and an orbital launch vehicle), of which the smallest one is expected to have its maiden flight this month.
Liftoff of Stardust 1.0!Top-down view from the launch tower.
I've left out another one. The Dutch/New Zealand: Dawn Aerospace mk.II Aurora (and mk.III) rocketplane(s)The mk.II Aurora can launch a 3U payload to >100km for 150s micro gravity, probing of the atmosphere or hypersonic flight.
IAF Member @SpaceForest2 Hybrid Rocket Engine SF1000 test No. 4 had many improvements like mass reduction of the combustion chamber, modified injector geometry, stabilization of engine working parameters and more. check out onhttps://youtube.com/watch?v=fnWAetWE6jE&t#IAFMembers